Thrombosis and osteoporosis prophylaxis

ABSTRACT

Use of a device to reduce risk of thrombosis and osteoporosis, which uses a pressure transducer to measure the forefoot force generated by a person with their forefoot, and generates a signal so that the person can recognize whether their forefoot force has reached a minimum value.

The invention relates to the use of a device for reducing the risk of thrombosis and osteoporosis.

Thrombosis is a frequently occurring condition in which a blood clot (thrombus) is formed in a vessel, usually a vein. The clot formation leads to a narrowing of the flow path and thus to a disturbance in the circulatory system. Clots may detach and become mobile. Thus, as a severe complication of a deep vein thrombosis (DVT), a massive pulmonary embolism with acute cardiac arrest could occur. In the case of an open foramen ovale (defect in the cardiac septum) a brain embolism, i.e., a stroke, is possible.

Thrombosis may result from an immobilization, such as during illness or after surgery. Increasingly, it occurs as the so-called traveler's thrombosis as, in the form of a deep vein thrombosis, and sometimes as deep vein thrombosis in the leg. When traveling in a car, in a plane or on a ship, a lack of exercise by the traveler, accompanied by a compression of veins, for example, the popliteal vein in the popliteal fossa (hollow of the knee) by the front edge of the seat, may lead to a reduction, in some cases a temporary halt, to the venous return flow from the feet and lower legs. As a result of this stasis, blood clots may form in the in the leg and pelvic veins. For air travelers, this phenomenon is known as the “Economy Class Syndrome” because the passengers now have too narrow seats with limited freedom of movement.

In recognition of this problem, passengers have attempted to increase the vitality of the flow in the leg veins, to thereby promote venous return. This can, for example, be accomplished by getting up and walking around regularly. The pressure on the feet and the activity of the leg muscles improves the blood flow (arterial as well as venous). The venous return is promoted on the one hand by the compression of the vascular tissue at the soles of the feet (venous patellar plexus) and on the other hand by the contractions of the lower leg muscles. The existence of this fascia system plays of a role in the lower leg, wherein contraction of the muscles results in compression of the veins. In addition, venous one-way valves prevent blood from being carried distally, that is, away from the heart.

However, since in fully occupied airplanes, and particularly in the economy class, a frequent getting up is impractical because it disturbs the other passengers, other ways to prevent DVT are being searched for.

In DE 91 12 809 U1, therefore, a device to promote circulation in the legs is described, providing an arrangement of two pedals on a common axis, so that each pedal is pivotable about the axis against a spring force. Thereby the lower leg muscles, especially the calf muscles, are to be activated.

As has been found, however, that for an effective thrombosis prophylaxis it is not sufficient for the movement of the foot alone, it also requires a sufficient force be created to deal with the “calf pump” in order to safely counter thrombosis.

Powerful foot lifting exercises are not recommended, because expansion of the muscle within the constricted fascia of the front-side lower leg or shin might trigger the so-called “exertion- or exercise-induced compartment syndrome”.

Osteoporosis presents a problem similar to thrombosis. Osteoporosis also arises due to lack of physical activity, e.g., in the elderly. If bones are not challenged by muscle tension, they wither away. They are subject to osteoporosis and can break more easily. This bone loss occurs even under conditions of weightlessness. Astronauts must therefore undergo a daily exercise program for prevention of osteoporosis, wherein the impact of the forces of on the bones become as effective as physical activity performed in gravity.

An example of the age-independent development of osteoporosis on earth is through physical inactivity following months to years of confinement to bed or wheelchair.

An object of the present invention is, therefore, to reduce the risk of osteoporosis and also the risk of thrombosis, particularly in passengers on land, on ships and in aircraft.

According to the invention, the solution of the problem involves the use of device equipped with a force sensor, which via a pressure transducer detects the force generated by a person with their forefoot, and provides a signal that allows the person to recognize whether their forefoot generated force has reached a minimum value.

In a preferred embodiment of the method, the forefoot force is produced by the area of the “front ball” of the feet (the heads of the metatarsal bones, metatarsal bones) and toes.

In particular, the forefoot force is generated by flexing of the plantar muscles of the feet. This form of movement is a foot-and-toes extension that is associated with a strain of the calf muscles: thus, an actuation of the “calf pump” (the body's “secondary heart”). In a powerful plantar flexion against a resistance the plantar plexus is also at least partially compressed, so that an increase of venous return through a venous inflow from the plantar plexus is facilitated.

The forefoot force is produced through the calf muscles, in particular by contraction of the gastrocnemius muscle, the soleus muscle and the toe-flexing muscles produces.

As it turns out, the mere movement of the foot is not sufficient for the increase in blood flow required for prevention of thrombosis. A certain amount of forefoot force must be generated, and it is of great importance to determine the amount of forefoot force. Only thereby can the venous blood return be sufficiently increased.

The forefoot force should, in particular for thrombosis prophylaxis, be dependent on the weight of the person, and each plantar flexion should be at a factor of at least 10%, preferably at least 20%, and most preferably 30-70% of the body weight.

Since the force F (expressed in Newton (N)) is proportional to mass and is dependent on acceleration, on the earth the equation would be F=9.81 N.

A forefoot force produced at regular intervals with half the body weight per foot would give for a person weighing 60 kg on Earth at any one foot extension a forefoot force of 9.81×30, i.e., approximately 300 N.

The invention is particularly suitable for DVT prophylaxis. But it can be applied as well to thrombosis prophylaxis in bedridden or other mobility impaired people.

For prevention of osteoporosis a sufficient physical activity is also important.

The term “sufficient physical activity” is currently not well defined, but may be equated to “sufficiently on his legs and moving about”. “Sufficient” could correspond to an average number of steps of 5000-8000 per day.

At each step there is an applied load or tensioning of the forefoot at about 110% of the body weight, so at 8,000 steps a man weighing 60 kg: 66 kg×8,000=528,000 kg, or approximately 5.28 million N.

Generating a forefoot force can therefore also be used for prevention of osteoporosis, since the generation of a forefoot force at the same time produces the required effect on bone. For producing the forefoot workout, these step numbers can be simulated, even when sitting or lying down.

With the use of a device able to measure force in persons, there is the advantage that real physical performance, that is, force on the bone, is determined. Therein it is a big difference to the stress of the skeleton whether steps are made on a flat surface or whether, for example, one climbs a staircase.

According to a further embodiment of the invention is therefore envisioned that signal is generated upon reaching a predetermined cumulative forefoot force.

In practice, one would first measure the activity output of a person and then decide whether, for prevention of osteoporosis, an increase would be advisable. One could, for example, set as a value for the total forefoot force 330,000 kg, or 3.3 million N. A 60 kg person would then have to take 5000 steps per day for each leg, with a forefoot force of 66 kg, i.e., 5000×66 kg=330,000 kg or 3.3 million N. Upon reaching 330,000 kg, or 3.3 million N, a signal would be generated. In steps with greater forefoot force, such as climbing stairs, a signal would be generated after a smaller number of steps, that is, sooner, in comparison to steps made with less effort on a flat surface, in which case the signal would be generated later.

For a design of the pressure meter 1, there are several possibilities. If the pressure measurement is to be capable of being done anywhere, such as in passenger aircraft, it is recommended that pressure meter 1 be provided on the foot of the passenger. This can be accomplished, for example, that the pressure sensor 1 is mounted on or disposed in a sock which is pulled over the foot or shoe of a passenger.

The pressure meter 1 could however be attached to an appropriate place on or in a shoe, for example, on the sole of the shoe. As shoes, there are included among others easy donning shoes like slippers or galoshes.

With such a device can the person can move around freely and basically practice their thrombosis or osteoporosis prophylaxis anywhere. The forefoot 5 is simply pressed—with or without shoes—against a counterforce or abutment 4, so that the pressure sensor on the forefoot can sense the resulting force. As abutment 4, it would be possible to use the floor, as well as any footrests on seats in the row ahead in vehicles, or other immovable objects.

On the other hand, it may be advantageous not to place the pressure transducer 1 on the foot of a person, but to install it directly to an abutment 4 against which the person presses their forefoot 5. Such a device can, for example, be use by several persons in succession.

In accordance with a further embodiment of the invention, the pressure sensor with a measuring device 2 is connected to an indicator device 3. Thus, a signal can be transmitted to the person from the indicator device 3 upon reaching a predetermined forefoot force. The person can thus optimize the foot movements necessary for prophylaxis of osteoporosis and thrombosis, as the device accurately measures the forces required, and upon reaching a predetermined value, indicates this to the person. The person is informed as to the number of active plantar flexions and the number of repetitions needed to be carried out. They thus receive the assurance that the measures for prophylaxis of thrombosis and osteoporosis were properly and, above all, efficiently carried out.

The signal output by the indicator device can be configured acoustically, optically, or visually in a different way. A vibration signal has the advantage that it is less disruptive to others than, for example, an acoustic signal.

The invention will be described in detail in the following on the basis of actual test results as well as an illustrative embodiment.

TEST RESULTS

An investigation of the venous return was made by measuring the velocity of blood in the vein of the hollow if the knee (popliteal vein). The maximum retrograde flow velocity (Vmax) in cm/s was measured in the right popliteal vein using Doppler sonography at rest and during contraction of the calf muscles for foot extension in the supine and standing positions.

The experimental subject was a 67-year-old healthy volunteer of 60 kg and 171 cm in height.

The meter used was the ultrasound device LOGIQ 7 (General Electrics), 7.5 MHz transducer, 2D, color Doppler.

I. Doppler sonography in the supine position on a couch

a. multiple measurements at rest:

-   -   Vmax-individual values: 13.1; 10.2; 9.9; 11.3 cm/s:     -   Vmax mean: 11.1 cm/s

b. Measurement with foot extension against a personal digital scale positioned vertically at the foot of the couch:

-   -   with pressure of 13 kg: Vmax 54.4 and 77 cm/s     -   with pressure of 16 kg: Vmax 71.9 cm/s

As the results show, foot extensions against an abutment with a pressure of 13-16 kg increased the flow rate an average of about 6-fold (67.8 cm/s compared to 11.1 cm/s).

II. Measurement of the maximum retrograde flow velocity (Vmax) in cm/s in the right popliteal vein using Doppler ultrasound at rest and during regulated contraction of the calf muscles while standing

To determine the foot sole pressure of the right leg, the leg was placed on an electronic personal scale, and the other leg was fully loaded. In this way a weight of the remaining leg of 6.2 kg was measured. This value was used as the null-value in the determination of the active weight.

a. multiple measurements at rest (i.e., simply stepping off of the leg from the bathroom scale):

-   -   Vmax-individual values: 7.7; 8.0; 8.5 cm/s:     -   Vmax-mean: 8.1 cm/s

b. Multiple measurements with foot extension against the scales with an active weight of 15 kg (i.e., after deduction of the leg weight of 6.2 kg there remained a net active weight of about 9 kg):

-   -   Vmax-individual values: 20.9; 30.0; 30.7; 37.2; 37.2; 30.7 cm/s     -   Vmax mean: 31.1 cm/s

The foot extension in the standing position against an abutment with an active weight of about 9 kg led on average to an increase in flow velocity by about 3.8-fold.

c. Multiple measurements with foot extension against the scales with a total weight of 20 kg (i.e., after deduction of the leg weight of 6.2 kg there remained a net active weight of about 14 kg):

-   -   Vmax-individual values: 39.8; 43.7; 64.0; 36.5; 18.3; 19.6;         21.2; 21.2 cm/s     -   Vmax-mean: 29.4 cm/s

The foot extension in the standing position against an abutment with an active weight about 14 kg led on average to an increase in flow rate by approximately 3.6-fold.

d. Multiple measurements with foot extension against the scales with a total weight of 25 kg (i.e., after deduction of the leg weight of 6.2 kg there remained a net active weight of about 19 kg):

-   -   Vmax-individual values: 42.4; 32.6; 41.8; 34.6; 43.7; 31.3; 34.6         cm/s     -   Vmax-mean: 37.3 cm/s

The foot extensions in the standing position against an abutment with an active weight of about 19 kg led on average to an increase in flow velocity by about 4.6-fold.

e. Multiple measurements with foot extension against the scales with a total weight of 30 kg (i.e., after deduction of the leg weight of 6.2 kg there remained a net active weight of about 24 kg):

-   -   Vmax-individual values: 36.5; 30.0; 44.4; 31.7; 46.3; 64.0;         60.7; 40.8; 65, 3 cm/s     -   Vmax-mean: 46.6 cm/s

The foot extensions in the standing position against an abutment with an active weight of about 24 kg on average led to an increase in flow velocity by about 5.8-fold.

The fact that in 9 kg and 14 kg active weight almost the same increase in flow velocity was found might be due to inaccuracies in the production of the intended active weight.

EMBODIMENT

The figure shows a device which can be used for prevention of thrombosis and osteoporosis. The foot of a person is here on a plate, which is an abutment 4. This foot is positioned such that the forefoot 5 touches a pressure sensor 1, so that a person can generate a forefoot force using the forefoot 5, which can be measured by the measuring device 2 via the pressure transducer 1. The measuring device 2 is connected to an indicator device 3, on which a signal can be displayed to the person, so that the person can see whether the generated forefoot force is sufficient.

In the example shown, the abutment 4 is rigid, so that a marked flexing of the plantar is possible only if the heel is raised. Thereby the knee is slightly raised or the passenger is pushed back a bit on his seat. This allows the blood flow in the leg veins, which had been impaired by the pressure of a seat edge, to be further improved.

The abutment 4 can be designed to be pivoted, to support in the entire foot while allowing flexing of the plantar. In this case it is advisable to so design the pivoting abutment 4 so that for example a strong and customizable restoring force acting against the forefoot force acts on the abutment 4. 

1-9. (canceled)
 10. A method for reducing risk of thrombosis and osteoporosis, comprising providing a pressure sensor (1) set to measure forefoot force produced by a person with his forefoot (5) and generate a signal that informs the person whether their forefoot force has reached a predetermined minimum value, and having said person repeatedly press against said sensor (1) with the forefoot (5) and generate said signal.
 11. The method according to claim 10, wherein the forefoot force is generated using the ball of the foot and the toes.
 12. The method according to claim 10, wherein the pressure sensor (1) is arranged relative to the person such that the force generated by the flexing of the plantar muscle and transmitted by the forefoot (5) is measured.
 13. The method according to claim 10, wherein the forefoot force is generated by contraction of the calf muscles.
 14. The method according to claim 10, wherein the forefoot force is generated by contraction of the gastrocnemius muscle, the soleus muscle or the toe-flexing muscles.
 15. The method according to claim 10, wherein the signal is produced upon reaching a given forefoot force which is programmed based on the weight of the person.
 16. The method according to claim 15, wherein said forefoot force corresponds to at least 10% of body weight of the person.
 17. The method according to claim 15, wherein said forefoot force corresponds to at least 20% of body weight of the person.
 18. The method according to claim 15, wherein said forefoot force corresponds to at 30-70% of body weight of the person.
 19. The method according to claim 10, wherein the signal is given upon reaching a predetermined cumulative forefoot force.
 20. The method according to claim 10, wherein the signal is visual, auditory, or kinesthetic.
 21. The method according to claim 10, wherein the pressure meter (1) is provided on or in a stocking or shoe.
 22. The method according to claim 10, wherein the pressure sensor (1) is located on a fixture against which the forefoot force is exercised.
 23. The method according to claim 10, wherein the pressure meter (1) is connected with a measuring device (2), and the measuring device (2) is connected with an indicator device (3). 